{"paper":{"title":"Observation of Galactic center in the sub-MeV gamma-ray band with electron-tracking Compton camera","license":"http://creativecommons.org/licenses/by/4.0/","headline":"A balloon-borne electron-tracking Compton camera detected gamma rays from the Galactic center in the 150-600 keV band at 7.9 sigma significance.","cross_cats":["hep-ex"],"primary_cat":"astro-ph.HE","authors_text":"Atsushi Takada, Kei Yoshikawa, Ken Onozaka, Mitsuru Abe, Taito Takemura, Tomonori Ikeda, Toru Tanimori, Yoshitaka Mizumura, Yuta Nakamura","submitted_at":"2025-09-19T10:42:46Z","abstract_excerpt":"We report the direct detection of gamma-ray emission from the Galactic center in the 150-600 keV band using the electron-tracking Compton camera (ETCC), which has a wide field of view of 3.1 sr. This represents the first application of this linear, imaging-spectroscopy method to observations of the Galactic center. Measurements in a one-day flight over Australia yielded significant gamma-ray detection in the light curve and revealed a $7.9\\sigma$ excess over the background in the image map from the Galactic center region. These results, obtained through a simple and unambiguous analysis, demon"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We report the direct detection of gamma-ray emission from the Galactic center in the 150-600 keV band using the electron-tracking Compton camera (ETCC)... revealed a 7.9σ excess over the background in the image map from the Galactic center region.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The background model and instrument response function accurately isolate the Galactic center signal without significant contamination from atmospheric or instrumental effects during the short balloon flight.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"The ETCC instrument detected a 7.9 sigma gamma-ray excess from the Galactic center in the sub-MeV band during a one-day balloon flight, with positronium flux consistent with INTEGRAL measurements.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"A balloon-borne electron-tracking Compton camera detected gamma rays from the Galactic center in the 150-600 keV band at 7.9 sigma significance.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"968264aa28c42f450d25c23c9ebb690f5dbf0cdac09e362e385f1b69f3dd7c0f"},"source":{"id":"2509.15851","kind":"arxiv","version":4},"verdict":{"id":"a25fb39b-33d6-48e1-9d76-3537e887b434","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-18T16:02:02.364738Z","strongest_claim":"We report the direct detection of gamma-ray emission from the Galactic center in the 150-600 keV band using the electron-tracking Compton camera (ETCC)... revealed a 7.9σ excess over the background in the image map from the Galactic center region.","one_line_summary":"The ETCC instrument detected a 7.9 sigma gamma-ray excess from the Galactic center in the sub-MeV band during a one-day balloon flight, with positronium flux consistent with INTEGRAL measurements.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The background model and instrument response function accurately isolate the Galactic center signal without significant contamination from atmospheric or instrumental effects during the short balloon flight.","pith_extraction_headline":"A balloon-borne electron-tracking Compton camera detected gamma rays from the Galactic center in the 150-600 keV band at 7.9 sigma significance."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2509.15851/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":1,"snapshot_sha256":"fd244acbeb26d0c07a1e4d087e122b88a9fd5bd6f4f13fecd2d9575054cfaceb"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}